This invention relates to the construction and use of pressure reservoirs and is particularly useful in pressure reservoirs of various types of life support systems and equipment related thereto. According to the pressure reservoir improvements of the present invention, a last-resort safety feature which is virtually incapable of deliberate or accidental frustration is directly incorporated in the pressure reservoir structure through the inherent formation and assembly thereof which will absolutely prevent reservoir contained fluid pressure rising above a predetermined maximum pressure always positively relieving pressures above the predetermined maximum. The result is that by properly selecting the materials from which the pressure reservoir is fabricated, and even though all other safety devices in the particular system fail, such as pressure safety valves or pressure blow-out plugs, the contained pressures within the reservoir can never rise sufficiently to cause accidental explosive disassembly or shattering which could endanger human life.
Various forms of fully portable, life supporting human breathing equipment have heretofore been provided and that most commonly used in recent times has generally included a relatively large and bulky compressed air reservoir or tank usually strapped to the back of the person using the system and having appropriate pressure reducing controls and face mask presenting air to the person in proper breathing form. For instance, such equipment has been used by firemen required to enter areas where the air is contaminated, other rescue personnel under the same conditions and underwater divers for both working and recreational purposes. The compressed air reservoirs of this form of equipment have contained compressed air stored at a pressure of two thousand pounds per square inch and due to the size and weight of the reservoirs, the persons using the same must be of relatively high physical dexterity.
With the advent of modern technology, however, the portable, life supporting human breathing equipment is fast progressing into the use of compressed air reservoirs of greatly reduced size and weight, along with greatly increased contained pressures. At the present time, the technology has increased to the point that maxiumum pressures of six thousand pounds per square inch of compressed air are permissible and used so that the same amount of human breathing air may obviously be contained in a compressed air reservoir of greatly reduced size. These smaller, high pressure, compressed air reservoirs are not only being designed into the human breathing equipment used by the personnel previously required to use such equipment, but have also opened up a quite large field of use for life supporting human breathing equipment by virtually anyone, regardless of size, in order to sustain their lives under emergency conditions.
In case of the firemen, other emergency personnel and underwater divers, with the smaller, high pressure, compressed air reservoirs, the same air supply may be provided in a greatly reduced size and bulk giving greater working freedom, or greatly increased breathing time may be provided while only approaching the size and weight of the prior reservoirs. At the same time, again due to the smaller, higher pressure, compressed air reservoirs, human breathing equipment may be provided for virtually anyone to sustain their breathing requirements for relatively short periods of time from say, a few minutes to nine or ten minutes. This means that with such short term, emergency human breathing equipment, many emergency situations that have previously caused the loss of life will no longer do so if the appropriate equipment is readily available.
Merely as an example of the great number of possibilities of use of the short term, human breathing equipment made possible by the smaller, high pressure, compressed air reservoirs and their related components, consider the possibilities of industrial accidents involving the accidental release of quantities of deadly fumes and gases. Where workmen are required to work in enclosed industrial areas, the normal atmospheric conditions thereof being perfectly safe for normal human breathing, but where deadly gases are present which, through control or transmitting type failure, quantities of the deadly gas can be released into the atmosphere by such an accidental failure, the provision of individual, portable, short term human breathing equipment readily available at each worker location can provide each workman with life sustaining breathing air of sufficient quantity for escape from the contaminated area. For instance, as soon as the accidental gas release occurs, each workmen would be trained to immediately locate and put on his individual human breathing equipment which would provide him with proper breathing air despite the surrounding deadly gas and it is only then necessary for him to move directly to a preplanned exit from the area within the next few minutes in order to be removed from danger. As stated, these individual, fully portable, short term human breathing assemblies can be of quite small size and relatively low weight so that the size and physical capabilities of the person using the same are really not an important factor.
Another example of possible use of these short term, fully portable, human breathing devices is in commercial aircraft accidents. It is well known that in commercial aircraft accidents, there are many occasions where a large number of passengers easily survive the initial impact but yet an ensuing fire within the aircraft will cause the death of a large number of these survivors merely due to the lack of life sustaining air during attempted escape. By the provision of one of these small human breathing devices at the location of each passenger seat and with previously given instructions, it is possible for each passenger to quickly put on and actuate the device to give them the few minutes of life sustaining breathing air in order to execute the escape from the burning aircraft.
Thus, the advancements in the portable, air breathing equipment field are providing quite practical and workable results in an ever expanding field of the preservation of human life, but one of the very important factors that must be kept in mind is the increase in problems of equipment design and fabrication resulting from the advancement from relatively low pressure, large and relatively heavy, compressed air reservoirs or tanks to the smaller, but quite markedly higher pressure reservoirs or tanks. Although any reservoir required to contain pressurized gas always presents certain serious structural problems from the safety standpoint, it is obvious that reservoirs operating at the present high maximum pressures greatly multiply the dangers involved. At a maximum pressure of six thousand pounds per square inch, failure of a reservoir by instantaneous partial disassembly or shattering is of a highly explosive nature quite seriously endangering human life and property and must be positively avoided.
Even though the various components of the higher pressure air breathing systems are necessarily of an advanced nature, various forms of safety devices are incorporated to meet the foregoing higher pressure containing problem. Pressure safety valves and/or pressure blow-out plugs are installed in the system, particularly the high pressure portion thereof, in order to relieve the pressure if the pressure should for some malfunctioning or accidental reason begin to build above a certain predetermined maximum spaced above the normal maximum operating pressure. For instance, with a maximum operating reservoir pressure of 5,000 pounds per square inch, the safety valve or blow-out plug would be set to release at a range in the order of 7,000 pounds per square inch to 7,500 pounds per square inch which, in turn, would be well below any pressures which would present the dangers of reservoir disassembly and shattering. Despite these safety devices, however, there still remains the possible dangers of safety device malfunctioning, accidental damage or deliberate tampering.